| Fibre-reinforced plastic laminates (FRP) have been widely used in many areas such as aerospace, offshore, naval architecture, transportation, chemical engineering, nuclear and defense industries. Since FRP laminates are complex both in its structure and material properties, projectile impact on such structures is a very complicated phenomenon involving many different energy absorbing mechanisms. Hence, it is very difficult to construct simple theoretical models which can cover all the effects observed in the impact process.This dissertation deals mainly with the peforation of fibre reinforced plastic laminates by flat-ended indentors/projectiles. Firstly,quasi-static penetration tests of relatively thin GFRP laminates are first carried out using flat-ended indenters in an MTS testing machine. The test results indicate that global deformation is the major energy absorbing mechanism of the thin GFRP laminates. Analytical solutions are derived for the deformation, penetration and perforation of composite plates subjected to quasi-static punch indentation. In particular, an equivalent strain failure criterion which takes into account the combined effects of transverse shear and global bending and membrane stretching on the perforation is proposed. From energy balance, an equation for quasi-static perforation energy is established which includes the energies dissipated by local indentation, local fibre fracture, delamination as well as global deformation. By introducing a dynamic enhancement factor (DEF), the quasi-static model is used to predict the ballistic limits for the perforation of thin FRP laminates subjected to impact by flat-nosed projectiles at normal incidence. It is shown that the present models are in reasonable agreement with available experimental results in terms of load-deflection curve, peak load, perforation energy and ballistic limit.Secondly, the penetration and perforation of thick FRP laminates struck transversely by projectiles with different nose shapes has also been theoretically investigated. Based upon the assumption that the deformation and failure is localized, the mean pressure offered by the FRP laminate targets to resist the projectiles can be decomposed into two parts: one part is a cohesive qusi-static resisitive pressure due to the elastic-plastic deformation of the laminate materials and the other is a dynamic resistive pressure arising from velocity effects. Furthermore, it is assumed that the resistance of the FRP laminates is no longer a constant, but a function of penetration velocity. Equations are obtained for predicting the depth of penetration, the residual velocity and the ballistic limit in the case of perforation. It transpires that the theoretical predictions are in good correlation with available experimental data in terms of penetration depth, residual velocity and ballistic limit.A preliminary study is conducted on the the transition between the local failure mode and the global deformation failure mode of FRP laminates by using Von Karman critical velocity. Though many assumptions and simplifications are introduced into the analysis the preliminary results seem encouraging. More studies are needed so that a comprehensive treatment on the subject can be found.Finally, based on the continuum damage mechanics, an orthotropic damage constitutive model for fiber-reinforced plastic laminates is adopted. The basic assumption of the model is that the stress-strain relationship of the laminate material can be described by linear elastic equations and that all the nonlinear behaviors of the laminates result from the damages. Numerical simulations with ABAQUS/VUMAT into which an orthotropic damage constitutive model is incorporated are performed to study the penetration and perforation of FRP laminates struck normally by flat-ended projectiles. Some preliminary results of the numerical simulations are presented and compared with some available test data. Reasonable agreement is found.
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